Homologous and Analogous Traits

Homologous Trait Between Humans and Felines  

 

When taking a look at felines and humans one may notice the similarities between the limbs and feet. Both humans and felines are mammals, which means both have a skeleton made from bone, are warm blooded, have a presence of hair/ fur and glands specialized to produce milk, known as mammary glands.

These creatures both share the characteristic of limbs and feet, these body features allow both mammals to stand, walk etc. Humans walk upright on two feet, people use their legs to complete tasks such as walking, running, jumping and standing, these limbs must be able to support the weigh of the person. Felines are digitigrades, which is an animal that stands or walks on its toes. Unlike most mammals, when cats walk, they move the two legs on one side of the body before the legs on the other side. Felines two back legs allow falling and leaping far distances without injury. Both limbs although very similar, the differences reflect the differences in lifestyles by both species.

The common ancestor between the feline and human would be a tetrapod that evolved to live on land. We can estimate that both animals share the same ancestor because both species come from are the same classification as mammals.

Analogous Trait Between Dolphins and Sharks

These creatures from the ocean both do look similar in structure but both bodies function differently from one other. Dolphins are mammals, their skeletons are made of bone, and they have to go to the surface for oxygen as well as they nurse their young. Sharks are cartilaginous fish which makes their skeletons made of cartilage, they use their gills to get oxygen and they do not nurse their young.

These creatures both share the body features of pectoral and dorsal fins to quickly swim through the ocean and catch prey. A shark's pectoral fins control the direction in which the animal swims and help maintain balance in the water. Pectoral fins help the shark make turns, swim up or down, and roll its body. Depending on the species, the pectoral fins are also usually the largest fins on a shark. Unlike the dolphin a shark has two dorsal fins, the first dorsal fin is located on the top of a shark’s back and is used to stabilize the shark and prevent the animal from rolling on its back and helps it make sharp turns while swimming fast. The second, much smaller dorsal fin is located on the back of the shark midway between the first dorsal fin and the tail. The second dorsal fin helps the shark swim steadily and maneuver the back of its body more easily. A dolphins pectorals help the animal to stop and turn, acting as balancing planes. They are the only of the dolphin fins to contain bone. An x-ray of the dolphin's pectoral fins reveals bones similar to those found in the human arm, wrist and hand. The dorsal fin is located on the top of the dolphins back, it is used to keep the animal upright and prevents the dolphin from rolling. Also it has a body temperature adjustment function, should the animal become overheated, and the dorsal fin serves to release excess body heat to the environment.

The closet common ancestor to the shark and dolphin would have the feature of aquatic vertebrate that evolved the aquatic body to from fins and flippers. We know that these traits are not directly related because ancestors of sharks remained aquatic creatures, while descendants of dolphins evolved to land creature then back to the aquatic creatures.